Air conditioning large commercial or industrial structures historically was accomplished by circulating large volumes of air by means of fans positioned to exhaust the interior hot air through an elevated opening, and by drawing in cooler outside air through openings in the walls of the structure, often through open windows. Such systems provided little, if any, control of the quality of the incoming air, and provided only limited relief from extreme heat as the air being drawn in was hot to start with, and moreover, depending on the nature of the commercial or industrial activity and machinery utilized, such activity very often generated considerable heat as well to the interior spaces of the building. As a consequence manufacturing operations historically were typically located in temperate areas to avoid "sweat shop" conditions during the heat of the summer months.
With the advent of cheap and abundant electricity, cooling of large buildings by electrically operated air conditioning systems became feasible and has been widely used. Though often requiring a substantial amount of electrical power during periods of high temperatures, i.e. daily temperatures exceeding 90 degrees Fahrenheit, air condition systems have become popular in temperate zones, and have permitted relocation of an increasing number of commercial and manufacturing operations to the so-called "sun belt", to enjoy the benefits of a mild winter without the having to suffer the summer "sweat shop" conditions.
More recently, two conditions affecting electrical power have had an adverse effect on air conditioning large structures, particularly in the so-called "sun belt" localities. The first is that the cost of peak load power has risen dramatically, making air conditioning at peak load periods which coincide with the times of extreme heat very costly. Secondly, shortages of power now exist in selected areas of the country due to lack of generating capacity necessitating rationing of peak power and low power at peak load conditions experienced during periods of excess heat. The net result of these two conditions is that increasingly, commercial facilities are curtailing use of air conditioning during times of extreme heat, to the detriment of the working conditions for their employees, and at certain risk to stored or warehoused goods due to extreme heat and risk of associated fire.
It is therefore desirable to provide for an improved open-air heat exchange apparatus in combination with an air conditioning system to provide reliable, low cost air conditioning for large spaces utilizing an underground heat exchange system having controls to insure improved air quality.